The introduction of handheld and portable devices (e.g., mobile phones and tablet computers) has changed the way people view media. With these devices, bright text, images, and video content is viewed throughout the day. Typically, most of these devices are based on color generating displays (for example, liquid crystalline or organic light-emitting displays). In addition, personal media displays are also used in industrial, medical, or manufacturing settings.
One unintended consequence of viewing these displays is greater exposure to light. It has been found that certain wavelengths of light are projected to regions of the central nervous system responsible for the regulation of circadian rhythms. One downstream molecule that regulates circadian rhythms is melatonin. Melatonin expression is lower during the waking hours and increases shortly before and during sleep. It has been found that blue light suppresses the production of melatonin. For users reading or observing content in the evening hours, this can have the consequence of delaying the onset of sleep. This is particularly an issue for handheld displays due to their closer viewing distance to the eyes. For most users, this may only be a minor inconvenience; however, the dysregulation of circadian rhythms can produce sleep irregularities and is thought to contribute to the development of disorders such as insomnia and diseases such as obesity, diabetes, and others.